How Solar Energy Works – Part 2

Turning Solar Energy Into Electricity For Your Home

(Note: If you missed part 1 of this simple-language guide to how solar energy makes electricity – click here to get caught up.)

To recap quickly what we’ve learned so far:

The sun’s energy, in the form of light, causes electrons to escape from the silicon atoms in the solar panel. Those electrons travel down wiring to produce current, which is simply the flow of electrons.

So now the question is, how does this current actually power your home?

Voltage and Power – Forcing Electrons to Move

Solar panels have metal plates in them that collect the freed electrons. This also helps create what’s called an “electric field,” which produces voltage.

Voltage is best described as a force that pushes electrons. More voltage means more force. (It also means more danger, but high voltages are necessary to push electric current across the many miles of wiring that cover the modern world).

For a little math, voltage (V) times current (I) equals power (P), or, V * I = P

Voltage is measured with volts, current with amperes (amps), and power with Watts.

So when you hear about solar power systems like a 5kW solar array, this means that solar system produces 5 kilowatts (5000 Watts) of power every hour.

More voltage means more power, as long as it has the current to go with it. If the sun sets, then you’ve lost your source of energy, and the current stops. So the voltage produces no power, because it has no electrons to push.

That physics stuff can be tough, so hopefully you’re still with us. If you are, we’re almost done.

Solar Energy Produces Direct Current. Your Home Likes Alternating Current.

Who wins? Your home, of course. Otherwise you’d have no power. The power companies across the US and Europe all use alternating current (AC), because it’s way cheaper and in general also much safer.

The problem is, solar panels produce direct current (DC), which isn’t compatible with the outlets in your house.

For example – take a look at your vacuum cleaner. When you plug it in, the cable operates on AC, and so does the outlet you plug it into. But none of that will work if you have solar power, unless we can turn the DC from the solar panels into AC.

And that’s what an inverter is for. And every solar panel installation has to include an inverter for this reason.

But what is DC and AC?

Remember current? It’s the flow of electrons. If the electrons only flow in one direction, that’s direct current. This is the kind of electricity Thomas Edison first harnessed.

Alternating current is when the direction of current flip-flops like a politician. It’s more complicated to set up, but it’s less costly and more safe. In the US, current is regulated to change directions 60 times per minute, or once a second. In Europe it’s different, which is why your electrical devices don’t work if you take them overseas. The alternating of current happens within the wiring in the various power cords you plug in. Within those cords are two wires, and electrons can flow in either direction down both wires.

To produce usable solar power, an inverter takes the DC produced by the solar panels, and converts it into AC.

Solar panels are like batteries, in a sense. Batteries also produce direct current. But batteries are directly powering various devices, and no wiring is needed. But if you wanted to convert the power from your battery and somehow adapt it to your other electrical devices, you’d need an inverter to do it.

Using and Measuring Your Solar Powered Electricity

how solar energy makes electricity - manual electricity meterFor the last step, the inverter now sends the usable AC power to an electric service panel, which can then route the electricity to the various home circuits where it’s needed.

Your electric meter then measures how much electricity you’re using. You’ve probably seen one of these before, because every house has one.

If the energy you need to run your home is more than the solar panels are producing, then the meter will draw power from the normal power grid.

On the other hand, if your system produces extra energy, more than you need for your house, then you have a few options, and this depends on what state you live in too, because not all states have the same allowances.

But if your solar energy system produces extra power, you have 3 main options:

  • Store it in a solar battery and use it at night or during a power outage (get the full guide to solar power batteries)
  • Send it back to the grid. This is what net metering makes possible, but again, not every state (or city) allows it. Some places allow you to actually sell your excess power to the grid, so you make money.
  • Just do nothing and enjoy your free electricity while you have it

And that’s it! You now have a basic understanding of how solar energy makes electricity.

Most of the complicated science and strange and complex details of how solar energy works have been left out. With this basic understanding of the raw science behind solar energy, you can build on it as you continue to learn more.

And again, if any part of this 2-part guide was too hard to understand – even for a 6th grader – please let us know, tell us which part, and we’ll find a simpler way of explaining it.


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